Wastewater Characteristics Characteristics are categorized as: Physical Chemical Biological Concentrations characterize wastewater as: weak, medium, and strong.

Physical Characteristics Solids - Total solids: residue after evaporating all water (50% volatile and 50% fixed) (Volatile=organic. Fixed=inorganic mg/L) - Suspended solids: residue retained on a filter (75% volatile and 25% fixed). - Dissolved solids: residue passing through a filter (40% volatile and 60% fixed). - Settleable solids: residue after one hour settling in an Imhoff cone (ml/L) (the indicator of primary sludge).

Chemical Characteristics Organics: Predominant biodegradable fraction, BOD -Protein -Fats, Oils, and Greases -Carbohydrates -Surfactants (detergents) -Urea Priority pollutants Industrial solvents, pesticides, etc. Pre-treatment standards control concentrations to trace levels

Chemical Characteristics cont. Inorganic Matter Nitrogen: from protein and urea. NH2, NH3, NH4+ forms ammonia and organics. An essential nutrient for growth of bacteria. Oxygen Demand: NH4+ + 2O2 = NO3- + 2 H+ + H2O

Chemical Characteristics cont. Phosphorous: phosphate (PO4-3) Inorganic-detergents organic-food and metabolic wastes Trace nutrients: S, Fe, Mn, Mg, Ca, K, Zn, Mo, etc. . . . . . plentiful

Biological Characteristics “Most” microorganisms known to microbiologists can be found in domestic wastewater. Bacteria Protozoa Viruses Algae (limited)